This study found that the presence or absence of a heart murmur does not reliably predict cardiac disease in cats.
Why they did it
Dyspneic cats may have underlying congestive heart failure, but is there a way to determine the presence of this life-threatening cardiac condition without the need for performing echocardiography? These researchers sought to determine if calculating a cat’s vertebral heart scale (VHS) might be a good indicator.
What they did
Researchers evaluated the medical records of 67 cats that were presented over a one-year period for evaluation of acute onset of respiratory distress. Inclusion in the study required thoracic radiography and echocardiography, and the VHS was calculated by two investigators for each cat. The VHS for normal cats is roughly < 7.3 on the lateral view of the thorax.
What they found
Researchers found that a VHS cutoff of > 8 vertebrae had a high sensitivity for screening for heart disease and that a cutoff of > 9.3 vertebrae had the highest specificity for a diagnosis of heart disease. For patients with a VHS between 8 and 9.3, researchers were unable to reliably predict whether heart disease or respiratory disease was the cause of the dyspnea. Echocardiography would be required for these cases.
The presence or absence of a heart murmur does not reliably predict cardiac disease in cats. In addition, the variable appearance of cardiogenic pulmonary edema on thoracic radiographs may also make the diagnosis of cardiac disease difficult. For cats seen on an emergency basis in which echocardiographic evaluation is not possible, VHS may aid in the differentiation of dyspnea due to cardiac disease vs. noncardiac causes.
Sleeper MM, Roland R, Drobatz KJ. Use of the vertebral heart scale for differentiation of cardiac and noncardiac causes of respiratory distress in cats: 67 cases (2002-2003). J Am Vet Med Assoc 2013; 242(3):366-371.
Link to abstract: http://avmajournals.avma.org/doi/abs/10.2460/javma.242.3.366